I had the same problem, but only the system can't boot from legacy mode, not UEFI, if you have a system installed and boot from legacy mode, then try to switch to UEFI mode from BIOS settings, and then create a UEFI bootable Windows installer usb stick, re-install the Windows.

My problem is here, indeed before upgrade BIOS, the system worked well with both x86 and x64 system, that probably a BIOS issue.